Various methods of making lead acid storage batteries with a gelled electrolyte have heretofore been proposed. For example in U.S. Pat. No. 3,765,942 there is disclosed a lead acid battery in which each electrode is wrapped in a web of fiberglass and the gel electrolyte consists of a mixture of sulfuric acid and phosphoric acid and silicon dioxide as the gelling agent. The electrodes are charged and dried, then wrapped in the fiber web and assembled into the battery housing after which the gel electrolyte is introduced into the housing under vacuum and the housing is ventilated.
Other methods of gelling of lead-acid cells are disclosed in U.S. Pat. No. 4,414,302. The process described in this patent is applicable to either wet discharged electrodes or dry discharged electrodes. In one example the cell was made operative in accordance with the prior art by filling with dilute sulfuric acid and subsequent charging. In this example it was stated to be immaterial whether for setting into operation the cell was equipped with plates already charged in dry state or with non-activated plates so that the setting into operation constitutes the activation of the plates within the cell box. The cell was then discharged with the 20-hour current I.sub.20 =12.5 A down to a consumption of 250 Ah. to decrease the acid density to a final value of 1.06 specific gravity. The amount of sulfuric acid corresponding to the withdrawn capacity is electrochemically bonded in the electrodes in the form of lead sulfate which is now inactive with respect to the gel formation. When the discharging is completed, the electrolyte moves freely within the cell and is removed therefrom by dumping. A suitable gelling agent such as finely dispersed silicon dioxide (AEROSIL 200) was added to the electrolyte removed from the cell. To improve the cycle life, phosphoric acid may further be added to the electrolyte removed from the cell. This mixture of electrolyte and gelling agent was subsequently filled into the cells of the lead acid storage battery as filler electrolyte. The plates in the storage battery were then recharged whereby the gel formation in the electrolyte was effected as the result of increasing sulfuric acid concentration formed by the recharge. After completion of the recharge, the sulfuric acid concentration in the electrolyte was obtained which corresponded to the working acid density of the storage battery. In the second example the cell was equipped with dry, discharged electrodes. The setting into operation took place directly by means of an electrolyte already containing silicon dioxide and acid and subsequent recharging of the electrodes.
While the foregoing methods have proved to be satisfactory, it will be noted that such methods require charging the element assembly on the plates twice. It is an object of the present invention to provide a process for gelling lead-acid storage batteries wherein no discharge is needed and no recharge is needed. By gelling on the formation charge it is only necessary to charge the element assembly on the plates once rather than twice, thus resulting in a saving of time.